The present invention relates to an apparatus for inspecting bottles, particularly to an apparatus for detecting defects such as a crack, chipping and contamination at the neck and threaded portion thereof of glass bottles which are conveyed on a conveyer.
A conventional bottle inspecting apparatus is disclosed in Japanese Laid Open Patent Application No. 58-34348 entitled "Apparatus for Inspecting Defects of Bottle Neck" filed by the present applicant. As shown in FIG. 1 the disclosed bottle inspecting apparatus mainly comprises bottle conveying means 70 for conveying bottles 1 to be inspected while rotating them; a pair of strip-like light sources 2 along the opposite sides of the conveying means 70 for illuminating the neck 11 and threaded portion thereof 12 of the bottles 1 to be inspected; and light detector means 3 having a field along a diameter line of the bottle neck 11 in alignment with the conveying direction of said conveying means for receiving the light which has been upwardly reflected by the defects and for converting the light into an electric signal.
In the present apparatus, the bottles 1 are conveyed on and along a conveyor 8 while being rotated by means of bottle rotating drive mechanism 7. At this time, the neck 11 and the threaded portion 12 thereof are illuminated by strip-like light sources 2 disposed at the right and left sides of the conveyor 8. Photoelectric transducers 3 comprising photo-diode array 320 are disposed so that they have an elongated field extending in a conveying direction the conveyor 8. The transducers monitor the conveyed and rotating bottle 1 during a half rotation thereof. If there is a defect 1a at the bottle 1 the light is scattered by the defect 1a. A part of the scattered light is directed upward and incident upon the photoelectric transducer 3. After the light is photoelectrically converted the electric signal is converted into digital signal by an analog/digital convertor 4. The digital signal is applied upon the defect detecting circuit 5. However the light may also be scattered by a line of juncture and the begining of the thread (close to the bottle finish of the bottle neck) so that the scattered light may be incident upon the photoelectric transducers 3 disposed above the conveyor 8.
Therefore the signals from the digitalizing circuit 4 include a signal due to defect 1a and a signal due to the line of juncture and the beginning of thread of the bottle 1. The defect discrimination circuit 5 measures the value representative of the area of defective portion and determines the signal exceeding a predetermined value caused by a defect to discriminate the defect 1a from the line of juncture and the beginning of the thread of the bottle.
Since the conventional bottle inspection apparatus has been formed as described above, it fails to find out small defects in the course of the separation between the signal due to defect and the signal due to the line of juncture and the beginning of the thread. The conventional bottle inspection apparatus has a disadvantage in that it does not have enough sensitivity to find the defect at the bottle finish having no line of juncture and the beginning of the thread.